1. Field of the invention
This invention relates in general to modifications of an airplane fuselage, and in particular to a method for shortening the forward portion of strakes on the forebody of an aircraft.
2. Description of the Prior Art
At times, it is desirable to modify the aerodynamic features of existing aircraft. For example, tests have determined that aerodynamic performance of an F-16 fighter aircraft may be improved by modifying the fuselage. This modification involves shortening the length of the strakes on both sides of the fuselage. The strakes are thin, narrow aerodynamic shapes that extend forward from the wings on each side of the forebody.
In the portion where the strakes would be removed, a number of intermediate frame members locate between two bulkheads. The frame members comprise curved beams in symmetrical pairs, each beam having inner and outer flanges separated by a web. The outer edge contour of each frame member is formed to provide support for the existing strake. The existing F-16 aircraft has aluminum skin panels that secure over the frame members and are contoured to provide the surface of the strake.
U.S. Pat. No. 4,869,443, Sep. 26, 1989, Andrew M. Skow, describes a method of modifying the F-16 fuselage to shorten the lengths of the strakes. The method of the patent teaches to extensively disassemble the existing structure around the crew station and install new parts, including new frame members. The method requires removing all of the intermediate frame members between the two bulkheads, intercostals, and other related attachments of crew station equipment and system supports. New frame members without the strake contour on the outer edges are then installed.
The complete removal of the intermediate frame members between the crew station forward and rearward bulkheads is particularly disruptive. The intermediate frame members provide support for numerous crew station equipment and system supports. Supports for throttle quadrant and cable mounts, electrical wiring harnesses, hydraulic and pneumatic tubing, environmental control systems routing, and flight control consoles are some of the attachments made to these intermediate frame members. The systems hardware must be detached prior to removing the intermediate frame members. Additional crew station equipment and systems, also unrelated to the original purpose of the retrofit, must be removed to provide adequate access to associated frame joints and system supports. During reconstruction, complex tooling is required to locate new frame members to re-establish aircraft contours within tolerances. Supplemental tooling is required to relocate system supports and equipment that was removed earlier. Further, many of these attachments must be electrically grounded for safety purposes, requiring extra testing equipment and skilled technicians to accomplish the task.